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Antimicrobial resistance
in Neisseria gonorrhoeae
David Lewis
National Institute for Communicable Diseases
National Health Laboratory Service
Johannesburg
South Africa
NHLS
NICD
NHLS
NICD
The First World War
•
Gonorrhoea control was based on:
- personal hygiene lectures
- weekly medical ‘visual’ examination of CSWs
•
Venereal ablution rooms established in all
barracks (1916) and soldiers at risk were
under order to attend within 24 hours
of potential exposure to N. gonorrhoeae
•
Self-administered regimen:
- wash genitals with soap and water
- irrigate the urethra with KMnO4 (“pinky panky”)
- apply calomel ointment to the whole area
•
Prophylactic “packets” (1917)
- calomel ointment to apply to the genitals
- tube of argyrol for the urethra (after coitus)
- condoms
Urethral dilators c. 1900
From Valentine (1900) “The irrigation treatment of gonorrhoea”
“Kollmann’s ingeniousness seems to have no limit”
Sulphonamides
•
Gerhard Domagk reported that Prontosil was
curative against haemolytic streptococci in
animals (1935) - he later used it with success
in humans
•
Prontosil released sulphanilamide - easily
manufactured
•
First studies using sulphanilamide in gonorrhoea
came from Germany, UK and USA (1937)
•
Cure rates for gonorrhoea rose to 80-90%
•
By 1944, treatment failures were common
Penicillin
•
Alexander Fleming published his discovery of
penicillin in 1929
•
Cecil Paine treated two babies with gonococcal
conjunctivitis with crude extract of Penicillium
notatum in 1930
•
Penicillin was first used to treat gonococcal
urethritis in 1943 (USA) – mainly troops
•
Cure rates with IM penicillin were >95%
MIC drift for penicillin against
Neisseria gonorrhoeae, USA (1955-69)
Initial studies in men undertaken to determine the minimal amounts of drug
and the shortest treatment period which would produce an acceptable cure rate
(20,000 U 3hrly x 6 doses = 72 mg; 15 hours treatment period)
0.05 U = 0.03 μg
0.5 U = 0.3 μg
Slyke et al., Am. J. Pub. Health. 1943;33:1392-1394
Martin et al. J. Infect. Dis., 1970:122:459-461
Slide courtesy of David Livermore, Health Protection Agency, UK (modified)
Chromosomally-mediated resistance
•
By mid 1950s, several reports of decreased susceptibility to penicillin
•
Chromosomal resistance reported in 1958
Low-level, multiple step resistance
penA
- 4-8 fold increase in penicillin MICs
- lowered affinity for PBP2
- shift to PBP1 target
mtr
- low level resistance to several Abs (Pen, Ery and Tet)
- altered cell envelope with decreased permeability
penB
- encodes for PorB1-b, porin
- 4-fold increase in penicillin and tetracycline MIC with mtr
pen A + mtr + penB gives 120-fold increase in penicillin MIC
ponA
- lowered affinity for PBP-1
penC
- efflux/permeability mechanisim (penicillin and tetracyclines)
Plasmid-mediated resistance
•
First reported independently in UK and USA in 1976
•
The 3.2 MDa African and 4.4 MDa Asian plasmids are identical except
for a 2.1 kb deletion
•
Require the 24.5 MDa conjugative plasmid for transfer
•
More plasmids were identified from the mid-1980s onwards:
Toronto 3.05 MDa , Rio 2.9 MDa, Nimes 4.0 MDa and New Zealand 6.5 MDa
100
PPNG prevalence (%)
90
80
70
1985
60
1990
50
1995
40
2000
30
20
2005
10
0
PPNG
1985
1990
1995
2000
2005
39
44
67
75
87
Rise in PPNG prevalence in
Cameroon (1985-2005)
Manuel de formation des prestataires de soins sur
la prise en charge syndromique des IST au
Cameroun. Ministry of Public Health, April 2007.
Tetracycline
•
Tetracycline was designed by chemical alteration of a microbial product (1952)
•
Chromosomal resistance soon followed (rpsJ + penB + mtr)
•
Plasmid-mediated resistance (TRNG), with MIC > 10 mg/L, first appeared in
the Netherlands (1985) and USA (1986)
•
Dutch and American TRNG strains had different phenotypes
80
Data from Gauteng Province
for 210 N. gonorrhoeae isolates
surveyed in 2008
Prevalence (%)
70
60
50
76%
40
30
Dutch plasmid
20
10
24%
American plasmid
0
TRNG
•
CMTRNG
Intermediate
Susceptible
Tetracycline resistance is now unacceptably high in most parts of the world
STI Reference Centre, National Institute for Communicable Disease, South Africa
Gentamicin
•
Gentamicin 240 mg i.m. has been used as national anti-gonococcal
first-line therapy in Malawi since 1993
•
Prescribed together with doxycycline in syndromic management
•
No standard MIC that defines resistance
•
Recent surveillance data from Malawi (2007) demonstrate that 100%
of isolates tested (n= 100) are susceptible based on agar dilution
results (MIC ≤ 4 mg/l)
•
Injectable agents less liable to abuse
Data courtesy of Irving Hoffman, University of North Carolina, USA
Malawi surveillance studies have been performed through a collaboration between the University of North Carolina,
the Kamuzu Central Hospital’s STI Clinic in Lilongwe and the Malawian Department of Health.
Spectinomycin
45
Pen
•
Developed and marketed specifically
for the treatment of gonorrhoea
•
Narrow MIC range related to efficacy
•
Resistance was described in 1973
and widespread by the early 1980s
Spectinomycin
40
Penicillin
35
Resistance (%)
30
25
Penicillin
• Spectinomycin
Resistance due to mutation in spc
locus - decreases sensitivity of 30S
ribosomal subunit to spectinomycin
20
15
10
Spectinomycin
5
•
Major outbreak of spectinomycin
resistant gonorrhoea among US
military in Korea in 1987 after only
6 years’ use
•
Still has a key role in selected cases
0
1980
1981
1982
1983
1984
1985
Year
Boslego JW et al., New Eng. J. Med. 1987;317:272-278
Quinolones
•
Compared to nalidixic acid, fluoroquinolones have 100 x greater activity
and broader spectrum by virtue of a fluorine atom at C6
•
Clinical failure of single dose 250mg ciprofloxacin was first reported in
London in 1990 – failures with the 500mg dose soon followed
•
Resistance in N. gonorrhoeae is associated with point mutations
resulting in amino acid changes in:
a)
b)
•
the A subunit (GyrA) of the DNA gyrase
the parC-encoded subunit of topoisomerase IV
Many countries have now stopped using quinolones to treat gonorrhoea
Rise in ciprofloxacin resistant gonorrhoea
WHO Western Pacific Region
Prevalence of QRNG in the WHO Western Pacific
Region
100
90
80
% resistance
70
Hong Kong
60
Japan
50
Phillipines
40
Singapore
Australia
30
20
10
0
1997
1998
1999
2000
2001
2002
2003
2004
WHO Western Pacific Region Gonococcal Antimicrobial Surveillance Programme (GASP)
Rise in ciprofloxacin resistant gonorrhoea
South Africa (2004-2007)
35
32%
Prevalence of Resistance (%)
30
29%
28%
25
2004
20
2005
15
10
17%
16%
2007
11%
N/D
7%
5
0
Johannes burg
2006
Cape Town
Lewis DA et al., Sex Transm. Infect. 2008;84:352-355
STI Reference Centre, National Institute for Communicable Disease, South Africa
Association between sexual orientation
and ciprofloxacin susceptibility profile
GRASP and GISP survey data
GRASP 2000-2008
GISP 2001-2007
The Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP) 2008, Health Protection Agency, UK
Gonococcal Isolate Surveillance Project (GISP) Annual Report 2007, CDC, USA
Association between HIV serostatus and
ciprofloxacin susceptibility profile
2007 surveys in Cape Town and Johannesburg
120
100
N = 191
N = 75
80
57%
Percentage (%)
60
71%
HIV negative
HIV positive
40
43%
20
29%
0
Susceptible
Resistant
Susceptibility profile to ciprofloxacin
Lewis DA et al., Sex Transm. Infect. 2008;84:352-355
p = 0.034
Azithomycin
•
The 2g dose has significant G/I side-effects (better with ER formulation)
•
Isolates with reduced susceptibility have been identified since 1997
•
Emerging resistance involves:
- bacterial efflux systems (mtrRCDE operon, mef genes)
- modification of ribosomal target (erm genes)
- single nucleotide mutation in 23S rRNA gene
•
A cluster of 6 gonococcal isolates with high-level azithromycin
resistance (MIC 4,096 mg/l) was detected in the UK in 2007
•
Heterosexually acquired, patients not previously treated with
azithromycin, identical on NG-MAST typing (ST-649)
UK Health Protection Agency Report 2008;2(14);4 April
Shift in GISP Azithomycin MICs (1992-2007)
N.B. In 2005, there was a change in medium used in GISP laboratories
which resulted in an observational shift in the MIC by one dilution
The Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP) 2008, Health Protection Agency, UK
Gonococcal Isolate Surveillance Project (GISP) Annual Report 2007, CDC, USA
Reliable management options at present
•
I.M. Cetriaxone 125mg or 250 mg stat.
•
Oral Cefixime 400mg stat.
•
•
•
•
Oral Cefpodoxime proxetil 200mg stat.
I.M. Cefuroxime axetil 1g stat.
Oral Cetfibuten 400 mg stat.
Oral Cefdinir 300-600mg stat.
•
Oral Azithromycin 2g stat.
•
I.M. Spectinomycin 2g stat.
Antibiotics used to treat GRASP and GISP
patients for gonorrhoea
100
Antimicrobials used to treat GRASP patients: 2000-2008
Percentage of GRASP patients
90
Antimicrobials used to treat GISP patients: 1988-2007
n=14,647
80
70
60
50
40
30
20
10
0
2000
2001
2002
2003
2004
2005
2006
2007
2008
Fluoroquinolones
Cephalosporins
Azithromycin
Doxycycline
Ampicillin
Other
Note: GRASP data include antimicrobial agents given simultaneously for chlamydial infection
The Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP) 2008, Health Protection Agency, UK
Gonococcal Isolate Surveillance Project (GISP) Annual Report 2007, CDC, USA
Prevalence of resistance to antimicrobial
agents in clinical gonococcal strains
isolated in Central Japan, 1999-2002
Gonococcal Phenotype
1999-2000
N = 91
2001
N = 150
2002
N = 221
PPNG
1.1%
0.7%
0.5%
TRNG (MIC ≥ 16mg/l)
2.2%
0.7%
0.5%
CMRNG Pen (MIC ≥ 2mg/l)
2.2%
59.3%
73.3%
CMRNG Tet (MIC ≥ 2mg/l)
11.0%
53.7%
68.8%
QRNG Levofloxacin (MIC ≥ 1mg/l)
27.5%
53.3%
78.3%
Cefixime decreased susceptibility (MIC ≥ 0.5mg/l)
0%
26.0%
30.3%
Ceftriaxone decreased susceptibility (MIC ≥ 0.5mg/l)
0%
0%
0.9%
Spectinomycin resistance (MIC ≥ 128mg/l)
0%
0.7%
0%
Ito M et al., Antimicrob. Agents Chemother. 2004;48:3185-3187
Decreased susceptibility to cefixime
•
Mosaic penA genes, which encode PBP-2, cause these raised MICs
•
Some of the regions within these mosaic genes show homology to the
penA genes of N. perflava (N. sicca), N. cinerea, N. flavescens and
N. meningitidis
Ito M et al., Antimicrob. Agents Chemother. 2005;49:137-143
•
Recently, another mutation in the ponA gene, which encodes for PBP-1,
has been identified in strains exhibiting decreased susceptibility to cefixime
(Leu 421 to Pro 421) - less significant than the mosaic penA changes
Takahata S et al., Antimicrob. Agents Chemother. 2006;50:3638-3645
Cefixime MIC (mg/l) and presence of the
mosaic penA gene, Japan (2002-2005)
160
140
120
mosaic penA
native
100
80
N = 621
60
40
20
0
Ochiai S et al., J. Clin. Micro. 2008;46:1804-1810
Critical parameters for β-lactam therapy
•
β-lactam efficacy depends on duration for which [free drug] exceeds MIC
•
Penicillin is 70-80% protein bound, so for gonorrhoea, ‘therapeutic time’ is:
Total [penicillin] > 4 x MIC for 7-10 hours
(i.e. more than two-fold dilutions higher)
•
Data from penicillin-based studies has been extrapolated to cephalosporins
•
Protein-binding and half-lives of cephalosporins differ
•
For cephalosporins, a ‘therapeutic time’ for at least 10 hours is required
to eliminate ≥ 95% of N. gonorrhoeae infections
Jaffe HW et al., Antimicrob. Agents Chemother. 1979;15:587-591
Deguchi T et al., J. Infect. Chemother. 2003;9:35-39
Cefixime MIC drift, GRASP (2008)
70%
60%
2004
2005
50%
2007
2008
2006
40%
30%
20%
10%
0%
MIC (mg/L)
0.002 0.004 0.008 0.015 0.03 0.06 0.125 0.25
12%
10%
8%
6%
4%
2%
0%
0.06
2004
2005
2007
2008
0.125
2006
0.25
MIC (mg/L)
Slide courtesy of David Livermore, Health Protection Agency, UK (modified)
The Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP) 2008, Health Protection Agency, UK
Ceftriaxone MIC drift, GRASP (2008)
MIC (mg/L)
Slide courtesy of David Livermore, Health Protection Agency, UK
The Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP) 2008, Health Protection Agency, UK
Effect of prescribing cephalosporins
on ciprofloxacin resistance (UK)
Antimicrobial prescribing practice 2003 to 2008
Flouroquinolones
% patients prescribed antimicrobial
90
30
Cephalosporins
% Ciprofloxacin resistance (>=1mg/l)
25
80
70
20
60
50
15
40
% resistance
100
10
30
20
5
10
0
0
2003
2004
2005
2006
2007
2008
GRASP - The Gonococcal Resistance to Antimicrobials Surveillance Programme; sentinel data
from 24 laboratories and 26 GUM clinics
Slide courtesy of Catherine Ison, Health Protection Agency, UK
The Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP) 2008, Health Protection Agency, UK
Potential solutions
Frapper fort, frapper vite (Ehrlich, 1913)
•
Cefixime for longer course: 3 days at 400 mg p.o.
•
Cefixime 800 mg, followed by 2 x 400 mg p.o.
•
Ceftriaxone 250 mg i.m., followed by 2 days cefixime p.o.
Introduce firebreaks
•
Rotate cephalosporins / spectinomycin / azithromycin @ 2g
•
Treat males and females, or index and contacts, differently
Slide courtesy of David Livermore, Health Protection Agency, UK (modified)
Multi-drug and extensively drug resistant
Neisseria gonorrhoeae (MDR-NG and XDR-NG)
Class I: Antibiotics currently recommended for gonorrhoea
• Injectable extended spectrum cephalosporins
• Oral extended spectrum cephalosporins
• Spectinomycin
Class II: Antibiotics used less frequently, or proposed for more extensive use
•
•
•
•
•
Pencillins
Fluoroquinolones
Azithromycin
Aminoglycosides
Carbapenems
Proposed definitions:
MDR-NG: resistant to ≥ 1 class I antibiotic + ≥ 2 class II antibiotics
XDR-NG: resistant to ≥ 2 class I antibiotics + ≥ 3 class II antibiotics
Tapsall JW , Ndowa F, Lewis DA, Unemo M (manuscript submitted)
Requirement for an integrated,
comprehensive prevention strategy
• Enhancement of national and international surveillance systems
• Avoid further loss in culturing capability for N. gonorrhoeae
• New strategies to prolong the usefulness of existing antimicrobials
• Implement screening of high risk individuals
• Ensure prompt and efficacious treatment is available
• Tighter control on ‘open market’ antibiotic access & quality control of generics
• Enhance proportion of sexual partners who receive treatment
• Re-vitalise condom promotion and behavioural change strategies
• Prioritise research on new therapeutic agents, e.g. anatomical site-specific
clinical efficacy studies, pharmaceutical drug design
• Higher priority for sexually transmitted disease control funding
Conclusions
•
The gonococcus is has repeatedly evolved novel and effective resistance
mechanisms
•
The creeping MICs of N. gonorrhoeae to cephalosporins is a prima facie
case of emerging resistance
•
History repeats itself and human beings have a tendency not to learn
•
Treatment options are now very limited and we need to reconsider the
wisdom of continuing to use single dose therapies
•
Extended regimens and firebreaks may assist in the short term
•
Multidrug therapy looks inevitable
NHLS
NICD
NHLS
NICD